Injection moulding machines particularly to the injection head thereof and to the injection moulds used therewith

ABSTRACT

The invention pertains to improvements to injection moulding machines, according to which said machine is provided with an easily removable injection head designed to contain a supply of synthetic resin material sufficient to mould a series of objects within a mould provided with a closing device.

United States Patent [191 Claes Oct. 2, 1973 1 INJECTION MOULDINGMACHINES,

PARTICULARLY TO THE INJECTION HEAD THEREOF AND TO THE INJECTION MOULDSUSED THEREWITH [76] Inventor: Karel Claes, Kuringersteenweg 285,

Hasselt, Belgium [22] Filed: June 10, 1971 [21] Appl. N0.: 151,806

[52] U.S. Cl 425/190, 425/245, 425/54,

425/191 [51] Int. Cl B291 U112 [58] Field of Search 425/190, 191, 192,

425/251, 245, 242, 178, 180; 249/54; 222/561, DIG. 7', 285/401 [56]References Cited UNITED STATES PATENTS 3,195,185 7/1965 Goffin et al425/190 1,575,688 3/1926 Joanides 425/180 X 3,189,945 6/1965 Strauss425/245 2,927,543 3/1960 Sherbody 1 425/190 3,076,225 2/1963 Sherbondy425/190 X 2,948,018 8/1960 Hintermann et a1.. 425/190 X 220,871 10/1879Rutschman 285/401 X 977,271 11/1910 Callaghan ZZZ/DIG. 7

FOREIGN PATENTS OR APPLICATIONS 740,386 11/1955 Great Britain 425/190Primary Examiner--.1. Spencer Overholser Assistant ExaminerDavid S.Safran AztorneyRichards and Geier [57] ABSTRACT The invention pertainsto improvements to injection moulding machines, according to which saidmachine is provided with an easily removable injection head designed tocontain a supply of synthetic resin material sufficient to mould aseries of objects within a mould provided with a closing device.

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INJECTION MOULDING MACHINES, PARTICULARLY TO THE INJECTION HEAD THEREOFAND TO THE INJECTION MOULDS USED THEREWITH The present invention relatesto improvements to injection moulding machines, particularly to theinjection head as well as the injection moulds used in conjunction withsuch machines.

More particularly the invention relates to injection moulding machinescomprising moulds for the moulding of objects of synthetic resinmaterial, such as dental prostheses.

A first object of the invention is to provide a design for saidinjection head which is specially adapted for very easy, fast andefficient mounting on, and dismounting from the body of the injectionmachine.

Another object of the invention is to provide an injection head, inwhich the filling cylinder is removable; capable of axial displacement;capable of being opened completely, and provided with a removable sealor packing, with a view to facilitating the removal and replacement ofsuch cylinders and the expulsion of the plastic injection materialtherefrom, as well as permitting simple and easy cleaning of saidfilling cylinder.

Another object of the invention is to provide an injection head in whichthe formation of air bubbles in the plastic material it totallyexcluded.

The present invention aims at providing an injection head, in whichplastic material may be introduced into the filling cylinder in theshortest possible time and in which empty filling cylinders may bereplaced very rapidly by previously filled cylinders, so as to permitseries production of moulded objects such as dental prostheses byrepeated injection of plastic material, while the latter is in thedeformable plastic condition, and in which said filling cylinder can becleaned very efficiently.

Another object of the improvements according to the invention concernssaid injection mould, more specifically the arrangement for sealing saidinjection mould.

This sealing or closing device is such that, as soon as the injectionoperation has been terminated, it permits the injection opening of themould to be sealed immediately by a very simple operation, so as toefi'ectively prevent reflux of the injection material and to maintainthe pressure within the synthetic resin material throughout thepolymerization thereof.

The arrangement permits very easy fitting and removal of the closingpart without requiring special tools; adhesion of the synthetic resinmaterial to the closing part is avoided and there will be nodifficulties in removing said closing part nor damage to the dentalprosthesis.

In order that the features and advantages of the present invention bemore readily understood, a preferred embodiment will be described morein detail hereinafter, without limiting the scope of the invention, withreference to the appended drawings, in which:

FIG. I is a schematical side-elevational view of a moulding press orinjection apparatus provided with an injection head according to theinvention,

FIG. 2 shows a plan view of the apparatus shown in FIG. 1;

FIG. 3 shows, on an enlarged scale, the part indicated in FIG. 2 by F3in lengthwise sectional view;

FIG. 4 is a view similar to FIG. 3, but showing the injection headremoved from the press;

FIGS. 5 and 6 are sectional views taken along the lines VV and VIVI,respectively, in FIG. 4.

FIG. 7 is a view as seen according to the arrow F-, in FIG. 6;

FIGS. 8, 9 and 10 are views similar to FIG. 3, but showing the injectionhead according to the invention in different positions with respect tothe injection mould.

FIG. 11 is a diagrammatic plan view of an injection mould arranged asaccording to the invention;

FIG. 12 is a view as seen in the direction as indicated by arrow F2 inFIG. 1;

FIG. 13 shows a closing part according to the invention in front view;

FIGS. 14 and 15 show the closing part of FIG. 3 as seen in the directionof the arrows F4 and F5 respectively;

FIG. 16 shows the same closing part as seen according to arrow F6 inFIG. 5;

FIG. 17 shows the same closing part as seen according to the arrow F7 inFIG. 6;

FIG. 18 is a view similar to FIG. 1, after insertion of the closing partin the appropriate place on the injection mould;

FIG. 19 is a view as seen according to the arrow F9 in FIG. 8.

FIGS. 1 and 2 show a suitable press or injection machine of a type knownin itself, said machine being mounted on a table 2, which also carriesan adequate support or pedestal 3 for carrying a mould 4, said supportor pedestal being, e.g., provided with pins 5 suitably located forholding said mould and preventing it from tilting during the injectionoperation, and for keeping the injection opening thereof in alignmentwith the injection channel of the injection head.

On the aforesaid pressure apparatus 1 there is mounted an injection head6 according to the invention.

As shown in FIG. 4, this injection head 6 mainly comprises a part 7 thatis fixed on said pressure apparatus 1, and a removable part 8.

The fixed part 7 in this case comprises a flange 9 fixed, e.g., by meansof screws or bolts or the like on the outer face of said pressureapparatus 1, said flange being suitably shaped for guiding a rod orplunger 10 for the expulsion of the material contained in the injectionhead.

Said flange 9 has a circular inner groove or slot 11 provided therein,the outer rim of said groove having inward projecting parts or teeth12-13-14 formed thereat.

The projecting end of said rod 10, as shown in the drawing, is providedwith a threaded part 15 which cooperates with a cylindrical nut 16 madeof a slightly compressible sealing material such as nylon or the like,said threaded part 15 being extended by a cylindrical part 17, thepurpose of which will be explained hereafter.

The injection head proper 8 mainly comprises a coupling part 18, saidcoupling part being provided with an axial bore comprising two parts,viz., a first part 19 provided at the forward end of said coupling part18, and a second part 20 provided at the backward end of said couplingpart 18, said second part having a diameter slightly larger than thediameter of said first part 19.

Finally, at its backward end said coupling part 18 is provided withthree outward projecting parts or teeth 21-22-23, the width of saidteeth being slightly smaller than the distance between any two of theinward projecting teeth 12-13-14 of the aforementioned flange 9.

As appears from FIG. 7, said teeth 21-22-23 are each provided with abeveled edge 24 facing towards the forward end of the injection head.

By this arrangement it is obtained, that the fastening of said coupingdevice 18 on the pressure apparatus, more specifically on theaforesaidflange 9, can be effected very easily and rapidly, simply byinserting said coupling part 18 in such a way, that said teeth 212- 2-23of said coupling part, after passing through the openings between theteeth 12-13-14 of said flange 9, are rotated so as to engage each behindone of said teeth 12-13-14 of said flange 9. Owing to the slope of saidteeth 21-22-23, the rotation of said coupling part 18 will cause thelatter to be firmly gripped and tightened in said flange so as to besecurely held in coaxial alignment with respect thereto.

Obviously the same effect could be realized with straight teeth21-22-23, provided the teeth 12-13-14 have beveled inner side walls.

Removal of such coupling part can simply be effected by rotating it inthe inverse direction so as to disengage said teeth 21-22-23 from saidteeth 12-13-14.

In said coupling part 18 a suitably shaped filling cylinder 25 can beinserted, said cylinder having an outer diameter approximately equal tothe diameter of said axial bore 19 throughout the major part of itslength. The backward end part 26 of said cylinder 25 has an outerdiameter which is equal, or approximately equal to the diameter of theafroesaid bore 20 of the coupling part 18, whereas the forward end ofsaid cylinder is provided with an external threading 2'7.

Screwed on said external threading 27, by means of an internallythreaded part 28, a cover or cap 29 is provided, said cover or caphaving a relatively small dimaeter central bore 30 provided therein, theforward extending part of said cover or cap having a disk-shaped sealingmember 31, e.g., made of nylon, removably fixed thereon, said sealingmember being provided with a central bore 32 held in alignment with saidcentral bore 30 in said cover or cap 29.

Finally in the hindmost end of said cylinder 25 a plug 33 is inserted,said plug being provided with a blind axial bore 34, the diameter ofwhich corresponds with the outer diameter of said extension 17 of saidrod 10.

The use and the operation of the injection head according to theinvention are very simple, as follows:

The moulds 4 to be filled by injection of synthetic resin material aresuitably placed inposition opposite the pressure apparatus 1, e.g., bymeans of said support or pedestal 3 and said pins 5, and an injectionhead 8 is secured on said flange 9. Fixing said injection head on saidflange is readily carried out in the way as described hereinbefore, byrotating the coupling part 18 so as to engage the teeth 21-22-23 of saidcoupling part behind the teeth 12-1- 3-14 of said flange 9, causing theextension part 17 of said plunger or rod 10 topenetrate in the centralbore 34 of said plug 33. This situation is represented in FIG. 8.

From this Figure it also appears that thecontent of the cylinder issufficient for successively moulding, e.g., six objects, in the presentcase dental prostheses, in six different moulds 4.

As shown in FIG. 9, when the pressure apparatus 1 is put into operation,the rod 10 moves forward and, owing to the tight fit of the sealing nut16 as well as the plug 33 within the inner wall of the cylinder 25,pushes the latter through the axial bore 19 of the coupling part 18 intoengagement with the mould 4, so as to firmly press said sealing part 31on said cap 29 against the front wall of said mould 4, th injectionchannel 30-32 being held in axial alignment with the injection openingprovided in said front wall.

The use of said sealing part 31 ensures effective sealing of thejunction between the passages thus aligned so as to prevent thesynthetic resin material from escaping sideways.

The situation shown in FIG. 10 is that which arises after two mouldshave been filled with synthetic resin material.

After the mould 4 has been filled with synthetic resin material the rod10 is drawn back, the cylinder 25 being compelled to follow thisbackward movement by friction between the part 16 and the inner wall ofsaid cylinder 25, so as to withdraw said sealing washer 31 from saidmould 4, the latter thus being liberated for removal and replacement bythe following mould. During this backward movement the plug 33 remainsin the position it had reached at the end of the forward-going stroke,so as to keep said synthetic resin material under pressure during thebackward stroke of the filling cylinder.

This arrangement permits filling several moulds, six in this example, inrapid succession, within a time sufficiently short to prevent thesynthetic resin material from hardening whereby said material would loseits usefulness.

When the cylinder 25 is empty while more moulds remain to be filled, therod 10 is drawn back into its backmost position; by means of thecoupling part 18 the injection head 8 is completely removed to receive anew previously prepared cylinder 25 with cover 29, whereafter saidcoupling part with said new cylinder is again fixed on said flange 9 inthe way as hereinbefore described.

Thus said coupling device permits easy mounting and dismounting of theinjection head by a very simple manual operation, while also serving asa guiding means for guiding the axial movement of the filling cylinder25.

This arrangement also permits ready replacement of cylinders 25, whereasthe sealing device 31 ensures complete seaing of the injection openingof the mould while the injection head 8 itself ensures'that during theinjection operation, said mould is tightly held upon said support 3.

This arrangement also permits several filling cylinders to be preparedby filling them with synthetic resin, the plug 33 serving as a bottomfor said cylinders, as both the cover 29 and the plug 33 are removable,the cleaning of such cylinders is quite simple, the more so as effectivepartial cleaning can already be achieved, in case a certain quantity ofsynthetic resin material should be left in the cylinder 25, by movingsaid plunger 10 throughout said cylinder into its forward end position,so as to remove all residual synthetic resin material from said cylinder25.

Finally owing to the use of the twofold sealing l6 and 33, preferablyensured by menas of material such as nylon which has the possibility ofdilating under the pressure as will be exerted by the rod on thesynthetic resin material, completely effective sealing will be achievedso as to avoid any reflux of the synthetic resin, the plug 33 beingalways kept in contact with said material even during the backwardmovement of said rod 10, it is very important that pressure shouldalways be maintained on said synthetic resin material, in order to avoidair entry and thr formation of air bubbles in the prosthesis. In fact,if during the backward movement of the rod 10 a separation werepermitted to occur between said plug 33 and said synthetic resinmaterial, air would be drawn in through the passages FIG. 11 shows aninjection mould 4 of a type known in itself, said moulding comprising,as usual, two parts 35 and 36 secured to each other by suitable meanssuch as screw-bolts 37.

In a way also known in itself, said injection mould 4 is provided withan injection opening 38 preferably having its axis coincident with thejunction plane between the two halves 35 and 36 of the mould.

Through this opening 38 the synthetic resin material used for mouldingthe dental prosthesis is to be injected under pressure.

After the mould has been filled the injection head of the injectionmoulding machine must be withdrawn from said opening 38, and evidentlyat that time said opening 38 must be sealed in order to prevent thesynthetic resin material from flowing back, and to maintain the pressurein the synthetic resin material throughout the polymerization thereof.

To this effect, as shown in the accompanying drawings, braces or clamps39 and 40 have been provided on either side of the injection opening,one on each mould half 25-36, in diagonal opposition with respect toeach other; L-shaped braces 39 and 40 are used in the embodiment shownand the face 41 in which said injection opening 38 is provided issomewhat recessed with respect to the plane 42 that faces each of saidbraces 39 and 40. Thus U-shaped spaces 43 and 44 are formed between eachof said braces 39 and 40, respectively, and the corresponding parts ofthe plane 42.

The closing part proper is in this case constituted by a slab 45 havingon one side a projecting part extending throughout the length thereof,so as to provide a roughly T-shaped appearance in cross-section, saidslab having a lower part 47 of reduced thickness, the transition betweensaid lower part 47 and the thicker upper part of said slab being formedby a sloping strip-shaped surface 48, said surface having a slantingposition with respect to the edges of said slab, as illustrated in FIG.13.

The slanting position of the beveled surface 48 with respect to theedges of the slab corresponds with the diagonally opposed positions ofsaid braces 39 and 40, as will appear hereinafter.

After the injection operation has been terminated, in order to seal saidinjection opening 38 it will be sufficient to simply lower said slab 45between said braces 39 and 40 and the corresponding faces 42 of theinjection mould 4, with the projection 46 directed towards the opening38. In this way said part 46 will be applied against the surface 41,when the slab 45 is inserted to a sufficient depth, i.e., when thebeveled surface 48 comes into contact with both the braces 39 and 40,said beveled surface will cause said projection 46 to be firmly pressedagainst the surface 41 so as to provide efficient sealing of saidinjection opening 38 without any special tool being required.

When after the polymerization of the synthetic resin material the mould4 is opened, said sealing part or slab 45 can be simply removed bylifting it out of the space enclosed by said braces 39 and 40.

Preferably the slab 45 will be made of polished metal so as toeffectively prevent adhesion of synthetic resin material; as removal ofthe slab is effected by a movement perpendicular to the injectionopening 38, damage to the dental prosthesis will be avoided under allcircumstances. Removal of the slab is effected by inverse movement withrespect to the insertion thereof and can also be effected without anyspecial tools. In fact, a light blow with any object at hand will besufficient to disengage the slab from the braces 39 and 40.

Thus a very simple and efficient closing device for sealing theinjection opening of moulds is obtained.

Evidently the embodiment described above has been given only as anexample; within the scope of the invention many modifications can bemade; thus said braces could be provided on either side of both halves35 and 36 of the mould, in which case the beveled surface of the slab 45would be horizontal instead of oblique; the braces 39 and 40 could havebeveled inner edges in which case the slab 45 would be shapedcorrespondingly, etc.

It is also possible to provide both braces 39 and 40, according to theinvention, either on part 35 or on part 36 of the mould.

Finally it may be observed, that in the embodiment illustrated saidbraces 39 and 40 are arranged for vertical insertion and removal,respectively, of the slab 45. It is of course equally possible toarrange said braces 39 and 40 for horizontal or oblique insertion andremoval of said slab.

The invention is not in any way limited to the embodiment describedhereinbefore as an example and illustrated in the accompanying drawings,but within the scope of the invention and the appended claims, suchinjection heads could be realized in many different shapes and relativedimensions.

What I claim is:

1. In an injection moulding machine having an injection head and a mouldadapted to receive injection material from said injection head, whereinsaid injection head comprises a pressure rod, a sealing member connectedto an outer end of said pressure rod, an extension part connected tosaid sealing member and extending beyond said sealing member, aremovable filling cylinder having an outer end with an opening directedto said mould, and a plug located in said cylinder adjacent an inner endthereof and having a blind bore, said extension part fitting into saidbore and inside said cylinder when said inner end is attached to saidmoulding machine.

2. A machine in accordance with claim 1, wherein said mould comprises acasing having an injection opening, braces located on opposite sides ofsaid opening, a cover fitting between said braces and adapted to claosesaid opening and means pressing said cover against said opening.

3. A machine in accordance with claim 2, wherein said braces extenddiagonally relatively to each other. 4 t

1. In an injection moulding machine having an injection head and a mouldadapted to receive injection material from said injection head, whereinsaid injection head comprises a pressure rod, a sealing member connectedto an outer end of said pressUre rod, an extension part connected tosaid sealing member and extending beyond said sealing member, aremovable filling cylinder having an outer end with an opening directedto said mould, and a plug located in said cylinder adjacent an inner endthereof and having a blind bore, said extension part fitting into saidbore and inside said cylinder when said inner end is attached to saidmoulding machine.
 2. A machine in accordance with claim 1, wherein saidmould comprises a casing having an injection opening, braces located onopposite sides of said opening, a cover fitting between said braces andadapted to claose said opening and means pressing said cover againstsaid opening.
 3. A machine in accordance with claim 2, wherein saidbraces extend diagonally relatively to each other.